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Publication numberUS7125521 B2
Publication typeGrant
Application numberUS 10/831,894
Publication dateOct 24, 2006
Filing dateApr 26, 2004
Priority dateJan 28, 2003
Fee statusPaid
Also published asUS6746966, US20040198017
Publication number10831894, 831894, US 7125521 B2, US 7125521B2, US-B2-7125521, US7125521 B2, US7125521B2
InventorsChung-Long Chang, Jui-Cheng Lo, Shang-Ting Tsai, Yu-Liang Lin
Original AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method to solve alignment mark blinded issues and technology for application of semiconductor etching at a tiny area
US 7125521 B2
Abstract
A method of unblinding an alignment mark comprising the following steps. A substrate having a cell area and an alignment mark within an alignment area is provided. An STI trench is formed into the substrate within the cell area. A silicon oxide layer is formed over the substrate, filling the STI trench and the alignment mark. The silicon oxide layer is planarized to form a planarized STI within the STI trench and leaving silicon oxide within the alignment mark to form a blinded alignment mark. A wet chemical etchant is applied within the alignment mark area over the blinded alignment mark to at least partially remove the silicon oxide within the alignment mark. The remaining silicon oxide is removed from within the blinded alignment mark to unblind the alignment mark. A drop etcher apparatus is also disclosed.
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Claims(10)
1. A drop etcher apparatus, comprising:
a control unit;
a dispenser tube having:
an upper end;
a semiconductor structure;
and a lower tip proximate an upper surface of the semiconductor structure;
a chemical reservoir partially filled with a chemical within the dispenser tube; the chemical reservoir having an initial upper surface; and
a dispenser line comprising a pressurized gas connecting the control unit to the upper end of the dispenser tube, wherein the control unit controls a flow of the pressurized gas to dispense a predetermined amount of a drop of the chemical to remove blinded alignment marks of the upper surface of the semiconductor structure, wherein the predetermined amount of the drop is dispensed through the lower tip of the dispensing tube to the upper surface of the semiconductor structure by exertion of pressure from the gas flowing through the dispenser line to the initial upper surface of the chemical reservoir;
a filter interposed in the dispenser line through which the gas flows to filter the gas;
a pressure regulator interposed in the dispenser line through which the gas flows to regulate the pressure of the gas; and
a high-speed shut-off valve interposed in the dispenser line through which the gas flows to regulate the flow of the gas, wherein the high-speed shut-off valve has a radius, and wherein the pressure regulator, the high speed shut-off valve, and the filter are external to the control unit;
wherein the upper surface of the semiconductor structure comprises an alignment mark area and a cell area, wherein the alignment mark area is spaced apart from a shallow trench isolation opening of the cell area, and wherein the lower tip of the dispensing tube is aligned with the blinded alignment marks of the alignment mark area.
2. The apparatus of claim 1, wherein the radius of the high-speed shut-off valve is from about 0.05 to 5.0 mm.
3. The apparatus of claim 1, wherein a distance between the lower tip of the dispensing tube and the surface of the semiconductor structure is from about 1.0 μm to 1.0 cm.
4. The apparatus of claim 1, wherein the control unit controls the predetermined amount of the drop to dispense based on a product of a length of time the pressure regulator applies the pressure to the gas, the radius-of the shut-off valve, and an amount of pressure to the gas the pressure regulator applies.
5. The apparatus of claim 1, wherein the lower tip has an inside diameter of from about 0.1 to 1.0 mm.
6. The apparatus of claim 1, wherein the lower tip has an inside diameter of from about 0.01 to 2.00 mm.
7. The apparatus of claim 4, wherein the amount of pressure to the gas the pressure regulator applies is from about 0.001 to 5.000 psi.
8. The apparatus of claim 4, wherein the amount of pressure to the gas the pressure regulator applies is from about 0.001 to 10.000 psi.
9. The apparatus of claim 4, wherein the amount of pressure to the gas the pressure regulator applies is from about 0.001 to 5.000 psi and flows through the dispenser line for from about 0.001 to 5.000 seconds.
10. The apparatus of claim 4, wherein the amount of pressure to the gas the pressure regulator applies is from about 0.001 to 5.000 psi and the length of time the pressure regulator applies the pressure to the gas is from about 0.001 to 10.000 seconds.
Description

This is a division of patent application Ser. No. 10/353,229, filing date Jan. 28, 2003 now U.S. Pat. No. 6,746,966, A Method To Solve Alignment Mark Blinded Issues And Technology For Application Of Semiconductor Etching At A Tiny Area, assigned to the same assignee as the present invention, which is herein incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to semiconductor fabrication and more specifically to alignment marks and semiconductor etching at tiny areas.

BACKGROUND OF THE INVENTION

Alignment marks are used to permit precise alignment of photolithographic masks with the wafer during masking steps to minimize misalignment between multiple layers. However, the alignment marks are ‘blinded’ after non-ODR shallow trench isolation (STI) chemical mechanical polishing (CMP) processes. This prevents transfer of the lower alignment mark to the next, upper layer, for example a metal layer.

An additional photolithography and etching step (ODR) are required to clear out the silicon oxide residue from the ‘blinded’ alignment mark field. This increases costs, increases the cycle time and manufacture loading. Further, the ODR approach is limited by the circuit design rule especially as the design rule passes 0.1 μm logic and beyond.

Blind alignment marks will become a critical issue in non-OD reverse tone photo/etch (ODR) processes after 0.1 μm and beyond shallow trench isolation (STI) CMP.

U.S. Pat. No. 6,194,287 B1 to Jang et al. describes an STI process and reverse mask to clear off alignment marks.

U.S. Pat. No. 6,080,635 to Jang et al. describes discloses a method to preserve alignment marks with STI processes.

U.S. Pat. No. 6,043,133 to Jang et al. describes a process to improve STI removal over alignment marks.

U.S. Pat. No. 6,015,744 to Tseng describes a clear out and alignment mark process.

U.S. Pat. No. 5,188,258 to Iwashita describes a quantitative fluid discharge device.

SUMMARY OF THE INVENTION

Accordingly, it is an object of one or more embodiments of the present invention to provide an improved method of unblinding alignment marks.

Other objects will appear hereinafter.

It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a substrate having a cell area and an alignment mark area is provided. The substrate having an alignment mark within the alignment mark area. An STI trench is formed into the substrate within the cell area. A silicon oxide layer is formed over the substrate, filling the STI trench and the alignment mark. The silicon oxide layer is planarized to form a planarized STI within the STI trench and leaving silicon oxide within the alignment mark to form a blinded alignment mark. A wet chemical etchant is applied within the alignment mark area over the blinded alignment mark to at least partially remove the silicon oxide within the alignment mark. The remaining silicon oxide is removed from within the blinded alignment mark to unblind the alignment mark. A drop etcher apparatus is also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate similar or corresponding elements, regions and portions and in which:

FIGS. 1 to 6 schematically illustrate a preferred embodiment of the present invention.

FIG. 7 schematically illustrates a drop etcher used with the preferred embodiment of the present invention.

FIG. 8 is an enlarged cross-section of FIG. 7 taken at the dashed circle labeled “FIG. 8.”

FIG. 9 is an enlarged cross-section of FIG. 7 taken at the dashed circle labeled “FIG. 9.”

FIGS. 10 a, 10 b and 10 c are respective graphs of: voltage vs. time on of the signal from the controller; pressure vs. time; and the chemical drop vs. time.

FIG. 11A is an enlarged schematic representation of a portion the drop etcher illustrated in FIG. 7 used with a blanket wafer monitor.

FIG. 11B is a graph of an etching profile of a blanket wafer monitor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The inventors have discovered a novel method to solve the alignment mark (AM) blinding issues that includes using a wet chemical solution to partially remove the oxide residue within the blinded alignment marks after STI CMP processing. Furthermore, the wet chemical solution oxide residue removal easily integrates into the subsequent silicon nitride (Si3N4 or SiN) strip step.

Initial Structure

As shown in FIG. 1, structure 10 is preferably a silicon substrate and includes an overlying layer 12 lining alignment marks 16 within alignment mark area 20. Layer 12 is preferably comprised of silicon nitride (Si3N4 or SiN) or polysilicon (having a thickness of from about 500 to 2000 Å) and is more preferably SiN as will be used for illustrative purposes hereafter. SiN layer 12 is preferably from about 100 to 2000 Å and more preferably from about 800 to 1100 Å thick.

Alignment marks 16 have a depth of preferably from about 1150 to 1250 Å and more preferably about 1200 Å. Alignment marks 16 have a width of preferably from about 7.8 to 8.2 μm and more preferably about 8.0 μm.

A shallow trench isolation (STI) opening 14 is formed through the SiN layer 12 and into silicon substrate 10 within cell area 18 that is spaced apart form alignment mark area 20.

Formation of Oxide Layer 22

To form the STI, a silicon oxide (oxide) layer 22 is formed over silicon substrate 10, filling STI trench 14 and alignment marks 16. Alignment marks 16 are filled by oxide layer 22 and by the oxide residue formed by the CMP of oxide layer 22 to form planarized STI layer 22′ (see below).

Planarization of Oxide Layer 22

Oxide layer 22 is then planarized, preferably by a chemical mechanical polishing (CMP) process to form planarized STI 22′ and filling (and ‘blinding’) alignment marks 16 with oxide 22″.

Use of Drop Etcher 40

As shown in FIG. 4, a drop etcher 40 (such as that shown in FIG. 7) is aligned and used to dispense a wet etching chemical 25 in the form of a drop 26 only over the oxide filled 22″ alignment marks 16 within alignment mark area 20. The planarized STI 22′ is not contacted with, or affected by, wet etching chemical 25. The tip 24 of drop etcher 40 is aligned with the ‘blinded’ alignment marks 16 by finding water notch or by pattern recognition (align cell pattern).

Wet etching chemical 25 is preferably hydrogen fluoride (HF) or buffered oxide etchant (BOE). If BOE is used, it has an oxide:SiN etching sensitivity of about 10:1 with an oxide etching rate of about 1400 Å/min. If HF is used, it has an oxide:SiN etching sensitivity of about 15:1 with an oxide etching rate of about 9000 Å/min.

As shown in FIGS. 7 to 9, drop etcher 40 may include a control unit 30 that dispenses a measured amount of wet etching chemical 25, preferably in the form of a drop 26, from within dispenser tube 34 (having inside diameter 52) through tip 24 to wafer 10 by using pressure 50.

Line 51 connects control unit 30 to the upper portion of dispenser tube 34 and through which line 51 a gas, such as preferably air or nitrogen (N2), is pulsed through a filter 60, a pressure regulator 62 and a high-speed shut-off valve 64 controlled 66 by the controller 30 or a timer.

FIGS. 10 a, 10 b and 10 c respectively illustrate: voltage vs. the amount of time on ton of the signal 66 from the controller 30 or a timer; pressure vs. time; and the chemical drop 26 vs. time wherein:
chemical drop 26=(ton*Xr**Xp***)
with the shut-off valve 64 radius (r) being preferably from about 0.05 to 5.00 mm and is more preferably from about 0.01 to 8.00 mm. *ton: time on of the signal 66 from controller 30 or timer**r: shut-off valve 64 radius***p: gas pressure after the pressure regulator 62

The time control is preferably from about 0.001 to 10.000 seconds and more preferably from about 0.001 to 5.000 seconds; the pressure control is preferably from about 0.001 to 10.000 psi and more preferably from about 0.001 to 5.000 psi; the tip 24 inside diameter 54 is preferably from about 0.01 to 2.00 mm and more preferably from about 0.10 to 1.00 mm; and the dispenser distance 70 is preferably from about 1.0 μm to 1.0 cm and more preferably from about 0.5 to 6.0 mm.

As illustrated in FIGS. 8 and 9 (and see FIG. 4), upon the application of gas pressure 50 onto the upper surface 72 of the chemical 25 within the dispenser tube 34, the pressure 50 of the gas expels a portion of the chemical 25 through the drop etcher tip 24 to form a drop 26 as the level of the chemical 25 within the dispenser tube 34 is lowered to the dashed upper surface line 74.

By the precise control of the gas pressure, time and size of the tips and nozzles involved, consistent deposits are ensured with a sped-up output while maintaining high quality and reduced waste. By increasing either the gas pressure, the time duration or the tip gauge (inside diameter 54), the size of the drop and hence the etch size will increase.

The tip 24 is preferably comprised of a non-reactive material such as polytetrafluorethylene (PTFE), perfluoroalkoxy (PFA), or polyvinyl chloride (PVC). For wet dip process optimization, the tip 24 preferably has: an outer diameter 56 of preferably from about 0.5 to 3.0 mm and more preferably about 1.0 mm; and an inner diameter 54 of preferably from about 0.5 to 0.7 mm and more preferably about 0.5 mm.

The tip 24 is preferably spaced from the upper surface of the structure 10 a dispenser distance 70 of preferably from about 1 μm to 1 cm and more preferably from about 0.5 mm to 6.0 mm.

In real process control, the drop 26 has an inner diameter 100 of from about 0.1 to 0.7 mm and an outer diameter of from about 1.0 to 3.0 mm (see FIG. 4). This ensures that the wet etching chemical drop 26 covers the oxide 22″ filled alignment marks 16 within alignment mark area 20 without impinging upon the cell area 18 and the STI 22′.

Etching of Oxide 22″ Within Alignment Marks 16

As shown in FIG. 5, the etching chemical drop 26 etches the oxide 22″ within alignment marks 16 so that preferably from about 80 to 90% of the oxide 22″ within alignment marks 16 is removed and more preferably from about 85 to 90% in from about 10 to 100 seconds and more preferably from about 30 to 45 seconds.

The remainder of drop 26 is removed before the SiN strip step (see below).

SiN Layer 12 Strip

As shown in FIG. 6, SiN layer 12 is then stripped and removed from silicon substrate 10 and from within alignment marks 16 using a SiN stripping process that is preferably a wet bench clean process. This also removes any remaining oxide 22″ from alignment marks 16 and any wet etching chemical 25/oxide 22 residue from silicon substrate 10. The SiN stripping process preferably uses H3PO4.

Thus, alignment marks 16 are now clear and transparent to the next formed layer, such as a metal layer, so that the alignments marks 16 are transferred to the upper, next formed layer and may be readily observed for continued fabrication.

FIG. 11A is an enlarged schematic representation of a portion the drop etcher 24″ illustrated in FIG. 7 illustrating the inside diameter (ID) and outside diameter (OD) of an etched opening 102 shown in dashed line after a drop 100 from drop etcher 24″ is released from drop etcher 24″ onto a monitor wafer's oxide layer 12″ over silicon substrate 10″. The ID and OD are plotted in FIG. 11B (see below).

FIG. 11B is a graph of blanket wafer monitor etch rate and etch profile (not in real application) where CPVC is chlorinated polyvinyl chloride and the mean of BOE of 2:1 is a mixed ratio of about 40% NH4F to about 49% HF 2:1.

Advantages of the Present Invention

The advantages of one or more embodiments of the present invention include:

  • 1. saves the time and expense of an additional ODR;
  • 2. the method is simple and inexpensive;
  • 3. the method is easy to integrate with the SiN stripping process;
  • 4. current dispenser technology is available for the drop technology used in the present invention; and
  • 5. increase STI CMP process merge.

While particular embodiments of the present invention have been illustrated and described, it is not intended to limit the invention, except as defined by the following claims.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US5158748 *Jan 17, 1991Oct 27, 1992Mochida Pharmaceutical Co., Ltd.Calibrated nozzle containing interior, exterior tube
US5188258Mar 29, 1991Feb 23, 1993Iwashita Engineering, Ltd.Apparatus reponsive to pressure of a medium which effects fluid discharge for controlling the pressure of the medium and the time the medium acts on the fluid
US5506142 *Sep 7, 1994Apr 9, 1996Dade International Inc.Probe wash for liquid analysis apparatus
US5736105 *Feb 9, 1996Apr 7, 1998Astle; Thomas W.Hollow pistons; cylinder channels connecting to moving plate
US6015744Nov 5, 1998Jan 18, 2000United Silicon IncorporatedMethod of manufacturing a shallow trench isolation alignment mark
US6043133Jul 24, 1998Mar 28, 2000Taiwan Semiconductor Manufacturing Company, Ltd.Method of photo alignment for shallow trench isolation chemical-mechanical polishing
US6060320 *Dec 5, 1997May 9, 2000Bayer CorporationMethod of verifying aspirated volume in automatic diagnostic system
US6080635Apr 27, 1998Jun 27, 2000Taiwan Semiconductor Manufacturing CompanyMethod of photo alignment for shallow trench isolation with chemical mechanical polishing
US6158269 *Dec 3, 1998Dec 12, 2000Bayer CorporationMethod and apparatus for aspirating and dispensing sample fluids
US6191000Aug 23, 1999Feb 20, 2001Macronix International Co., Ltd.Shallow trench isolation method used in a semiconductor wafer
US6194287Apr 2, 1999Feb 27, 2001Taiwan Semiconductor Manufacturing CompanyShallow trench isolation (STI) method with reproducible alignment registration
US6203759 *Apr 7, 1998Mar 20, 2001Packard Instrument CompanyMicrovolume liquid handling system
US6239301May 4, 1998May 29, 2001Zambon Group S.P.A.Using a cysteine derivative
US6521187 *Jan 21, 2000Feb 18, 2003Packard Instrument CompanyAutomatic microfluidic dispensers having piezoelectric transducers joined to glass capillaries used as aspirators or ejectors for fluids to wafer surfaces, with uniformity, high speed and accuracy
US6805175 *Jun 12, 2003Oct 19, 2004Symyx Technologies, Inc.Powder transfer method and apparatus
US6867050 *Aug 6, 2001Mar 15, 2005Academia SinicaApparatus and methods for chemical synthesis
US6881579 *Jul 30, 2001Apr 19, 2005Agilent Technologies, Inc.Apparatus for use in the analysis of nucleotide sequences
US6902703 *Feb 5, 2001Jun 7, 2005Ljl Biosystems, Inc.Delivering fluid to sample holder utilizing a pump connected to fluid source, conduit path extending from the pump to dispenser remains open and unconstricted between deposition of fluid aliquots
US20020168297 *Aug 13, 2001Nov 14, 2002Igor ShvetsFor dispensing and aspirating small volumes of liquids for use in High Throughput Screening (HTS), Polymerase Chain Reaction (PCR), combinatorial chemistry, microarraying, proteomics
US20030032189 *Nov 15, 2001Feb 13, 2003Lloyd Greg A.Method and apparatus for calculating dew point, method and apparatus for compensating for dew point, MOS gas sensor system, and fuel cell system
US20030109060 *Dec 7, 2001Jun 12, 2003Biosearch Technologies, Inc.Dispensing nozzle; controlling fluid flow
US20030161761 *Feb 28, 2002Aug 28, 2003Williams Roger O.Apparatus and method for composing high density materials onto target substrates by a rapid sequence
US20030170903 *Jan 27, 2003Sep 11, 2003Innovadyne Technologies, Inc.High performance, low volume, non-contact liquid dispensing apparatus and method
US20040037749 *May 5, 2003Feb 26, 2004Woodward Roger P.Fluid dispensing system and method includes a pump to aspirate and expel sample fluid, a fluid dispensing tip, and a metering station. The fluid dispensing tip includes a working fluid and an air gap where the air gap separates the working fluid
US20040166028 *Mar 1, 2004Aug 26, 2004Eppendorf Ag.Microproportioning system
US20040241050 *Jun 9, 2004Dec 2, 2004Cytologix CorporationRandom access slide stainer with independent slide heating regulation
US20050032241 *Feb 26, 2004Feb 10, 2005Coassin Peter J.Reagent dispenser and dispensing method
US20050095723 *Nov 4, 2003May 5, 2005Drummond Scientific CompanyAutomatic precision non-contact open-loop fluid dispensing
US20050106754 *Sep 1, 2004May 19, 2005Caren Michael P.Fabricating biopolymer arrays
US20050135972 *Aug 6, 2004Jun 23, 2005Ventana Medical Systems, Inc.Automated biological reaction system for consistently placing an amount of fluid on a slide
US20060002824 *Jun 6, 2005Jan 5, 2006Irm, LlcDispensing systems, software, and related methods
Classifications
U.S. Classification422/504, 257/E21.251, 73/864.01, 73/864.11, 73/864, 422/88, 422/67, 257/E23.179, 73/863.32, 422/513
International ClassificationG03F9/00, G01N1/32, H01L21/311, B01L3/02, G01N1/10, H01L23/544
Cooperative ClassificationG03F9/7084, G03F9/7076, H01L21/31111, G03F9/708
European ClassificationG03F9/70K4, G03F9/70K6, G03F9/70K2, H01L21/311B2
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